This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    BS base station    BW bandwidth    CSG closed subscriber group    DL downlink (eNB towards UE)    eNB E-UTRAN Node B (evolved Node B)    EPC evolved packet core    E-UTRAN evolved UTRAN (LTE)    FDMA frequency division multiple access    IE information element    LTE long term evolution of UTRAN (E-UTRAN)    MAC medium access control (layer 2, L2)    MM/MME mobility management/mobility management entity    Node B base station    OFDMA orthogonal frequency division multiple access    O&M operations and maintenance    PCI physical cell identity    PDCP packet data convergence protocol    PHY physical (layer 1, L1)    PLMN public land mobile network    RAT radio access technology    RLC radio link control    RRC radio resource control    RRM radio resource management    S-GW serving gateway    SC-FDMA single carrier, frequency division multiple access    SIB system information block    TDD time division duplex    UE user equipment, such as a mobile station or mobile terminal    UL uplink (UE towards eNB)    UTRAN universal terrestrial radio access network
The specification of a communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.6.0 (2008-09), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8),” incorporated by reference herein in its entirety.
FIG. 1 reproduces FIG. 4.1 of 3GPP TS 36.300 V8.6.0, and shows the overall architecture of the E-UTRAN system 2. The E-UTRAN system 2 includes eNBs 3, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs 3 are interconnected with each other by means of an X2 interface. The eNBs 3 are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to a S-GW by means of a S1U interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
In general, a registered owner of a home eNB may add subscribers to its user group, and it is members of the user group that are allowed access to the CSG cell. Because one or more home eNBs can be linked to form more than one CSG cell contiguous with one another, it is convenient to term such an arrangement a CSG network. That is, a CSG network is a network composed of one or more cells with access permissions managed at least partially by final consumers (end users). Those subscribers registered as members of the user group are called CSG members. That is, a CSG member is a wireless service (e.g., cellular) user registered to the CSG network by the CSG administrator. Once registered, the CSG member is allowed to access the CSG network. Those users or devices not registered to the CSG are not allowed access to it, hence the term closed subscriber group. In CSG networks, only the devices (e.g., UEs) that have been granted permission to access the CSG network may camp or connect to that network. Examples of CSG cells include a home eNB (e.g., LTE cells that are purchased and/or operated by the consumer), corporate cells (e.g., cells that are hired or owned by a company), and “commercial” cells (cells that are owned by retail companies, supermarkets, etc.). It is the responsibility of the CSG administrator to register a user as a CSG member. While the CSG network can quickly control and modify the subscribers that form its user group, as noted above access is restricted to registered subscribers and closed to other users.
Mobility of the user group members between the CSG network and other cells that are “open” (non-CSG cells, whether they be E-UTRAN, UTRAN, GERAN, or others, for example) is possible.
The concept of the CSG network may be considered useful in the context of, by example, a corporate or university campus or a retail establishment. For example, the corporation or university provides its employees/students with free or low cost access to the CSG by enrolling them in the appropriate user group while simultaneously restricting others (e.g., unregistered users and devices) from accessing the service (via the CSG network).
Of particular interest herein is the use of CSG idle mode mobility in E-UTRAN.
One issue that has been agreed to in 3GPP (RAN2#63bis) regards whether the UE should be informed about a possible PCI split. Various potential aspects related to this issue include: making the UE aware of the PCI split on a mixed carrier; fixing the split in the specification is not possible (flexibility is needed for different deployments); the PCI split shall be signaled by the home-(e)NBs on the mixed carrier (mandatory); may be sent by macro cells on the mixed carrier (optional); once the UE has read the PCI split from a CSG cell on a mixed carrier, it may assume this split for 24 hours for this carrier, PLMN wide scope; and information may be included in a SIB (e.g., SIB4 in LTE/E-UTRAN; which SIB to use in UMTS is still to be decided). In this context, a “macro cell” may be considered to be a non-CSG cell.
The above-referenced PCI split refers to a reservation of PCIs to be used for CSG cells in a CSG co-channel deployment, where of a total number of available PCIs (e.g., approximately 500 in E-UTRAN) some are reserved for CSG cells while the remainder are used for the macro cells (non-CSG cells).
Additionally, in connection with the mixed carrier deployment (i.e., CSG and non-CSG cells deployed on a same frequency and thus using intra-frequency cell re-selection mobility), it has been discussed that use of an “intra-frequency cell re-selection indicator” would be useful. This indicator would be used for indicating to the UE whether it is allowed to camp on a cell which is not ranked as a best cell according to a normal intra-frequency cell re-selection evaluation procedure.
The current understanding of CSG mobility is that if the UE has reselected to a CSG cell, for example, due to it being the best ranked cell, the UE would check if the CSG cell is listed in the UE's “whitelist” (if the UE has a whitelist). The whitelist is a list of CSG identities to which the UE has access (it may be referred to as a CSG allowed list). While the exact content of the whitelist is currently not specified, it may be assumed that it will include at least some of the following: carrier frequency, RAT, frequency band, physical cell ID (PCI), the CSG identity and possibly one or more additional parameters. If the CSG is not listed on the whitelist (or the UE has no whitelist), the UE cannot camp on the CSG cell. As a result, the UE cannot obey the basic intra-frequency cell re-selection rule of being camped on the best cell and, thus, would need to reselect away from the CSG cell and the associated frequency.
It is pointed out that the CSG ID is not the same as the network ID. Within a given network (e.g., identified with a PLMN) there may be one or more CSG cells. These CSG cells are identified with a CSG bit plus a CSG identity. The actual CSG identity may have several formats depending on the size (number of cells) that constitute the CSG. As such, it may be appreciated that a subscriber to one CSG in the network/PLMN may not have access to another CSG in the same network/PLMN. General reference in this regard may be made to 3GPP TSG CT WG1 Meeting #55, Budapest, Hungary, 18-22 Aug. 2008, C1-083596, “Definition of Variable length CSG id within the Cell identity”, Vodafone, Qualcomm, Telecom Italia.
The above-mentioned intra-frequency cell re-selection indicator would inform the UE if it would be allowed to camp on another cell on the same frequency, even though that other cell would not be the best ranked. If this is allowed (camping on the non-best cell), then the UE can evaluate its intra-frequency cell re-selection algorithm and reselect to the second-best ranked cell on the frequency. If this (camping on the non-best cell) is not allowed, the UE would have to reselect away from the current frequency layer, i.e., perform inter-frequency or inter-RAT cell re-selection.
As presently considered, the intra-frequency cell re-selection indicator would be cell specific and broadcast on the CSG cell. That is, the intra-frequency cell re-selection indicator would be broadcast in the target cell of the re-selection.
With regard to the use of a conventional UTRA cell re-selection indicator, 3GPP TS 25.304, V8.3.0 (2008-09) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; User equipment (UE) procedures in idle mode and procedures for cell re-selection in connected mode (Release 8), states in section 5.3.1.1:
When cell status “barred” is indicated,                The UE is not permitted to select/re-select this cell, not even for emergency calls.        The UE shall ignore the “Cell Reserved for future extension (Cell Reservation Extension) use” IE.        The UE is not permitted to receive any MBMS services.        The UE shall select another cell according to the following rule:        If the “Intra-frequency cell re-selection indicator” IE in Cell Access Restriction IE is set to value “allowed”, the UE may select another cell on the same frequency if selection/re-selection criteria are fulfilled.        If the UE is camping on another cell, the UE shall exclude the barred cell from the neighbouring cell list until the expiry of a time interval Tbarred. The time interval Tbarred is sent via system information in a barred cell together with Cell status information in the Cell Access Restriction IE.        If the UE does not select another cell, and the barred cell remains to be the “best” one, the UE shall after expiry of the time interval Tbarred again check whether the status of the barred cell has changed.        If the “Intra-frequency cell re-selection indicator” IE is set to “not allowed” the UE shall not re-select a cell on the same frequency as the barred cell. During an ongoing emergency call, the Intra-frequency cell re-selection indicator IE shall be ignored, i.e. even if it is set to “not allowed” the UE may select another intra-frequency cell.        If the barred cell remains to be the “best” one, the UE shall after expiry of the time interval Tbarred again check whether the status of the barred cell has changed.        
The reselection to another cell may also include a change of RAT.
Additional publications that are related to the various topics discussed above include:    3GPP TSG RAN WG2 #63bis, 29 Sep.-3 Oct. 2008, Prague, Czech Republic, R2-085921;    3GPP TSG RAN WG2 #63bis, 29 Sep.-3 Oct. 2008, Prague, Czech Republic, R2-085836; and    3GPP TSG RAN WG2 #63bis, 29 Sep.-3 Oct. 2008, Prague, Czech Republic, R2-08xxxx (Chairman notes).